Alert archive / Massachusetts / Flash Flood Warnings in 2018

Flash Flood Warning 25, NWS Boston/Norton, MA

August 12, 2018Bristol County, Massachusetts

NWS Boston/Norton, MA issued this flash flood warning at Aug 12, 2018, 5:03 PM EDT for Bristol County, Massachusetts. It was in force for 78 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 12, 2018, 5:03 PM EDT (21:03 UTC)
Expired: Aug 12, 2018, 6:21 PM EDT
In force: 78 min
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Flood severity: None

County Bristol County, MA

The radar

The Boston radar (KBOX), 21 km from the middle of the area, began a volume at 21:07 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Aug 12, 5:53 PM EDT	HEAVY RAIN 4	Swansea, MA	AMATEUR RADIO

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Chatham, MA (KCHH), launched 12:00Z, 9.1 hours before the alert went out and 100 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 206 J/kg
Mixed-layer CIN: -27 J/kg
Mixed-layer LCL: 790 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 83 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

094 
WGUS51 KBOX 122103
FFWBOX
MAC005-130000-
/O.NEW.KBOX.FF.W.0025.180812T2103Z-180813T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boston/Norton MA
503 PM EDT SUN AUG 12 2018

The National Weather Service in Boston/Norton has issued a

* Flash Flood Warning for...
  Central Bristol County in southeastern Massachusetts...

* Until 800 PM EDT.

* At 502 PM EDT Doppler radar indicated a heavy downpour over 
  Swansea moving slowly southeast. Flash flooding is expected to 
  begin shortly.

* Some locations that will experience flooding include...
  Somerset, Swansea and Dighton. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

A Flash Flood Warning means that flooding will occur quickly, and
could be life threatening for those who try to drive through flooded
roads or underpasses. Find alternate routes. Those near small streams
need to get to higher ground immediately.

&&

LAT...LON 4181 7117 4177 7111 4171 7117 4175 7123

$$

WTB

1 follow-up statement

975 
WGUS71 KBOX 122221
FFSBOX

Flash Flood Statement
National Weather Service Boston/Norton MA
621 PM EDT SUN AUG 12 2018

MAC005-122228-
/O.CAN.KBOX.FF.W.0025.000000T0000Z-180813T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Bristol MA-
621 PM EDT SUN AUG 12 2018

...THE FLASH FLOOD WARNING FOR CENTRAL BRISTOL COUNTY IS CANCELLED...

The heavy rain has tapered to light rain. Flooding is no longer 
expected to pose a threat. Please continue to heed any road 
closures. 

LAT...LON 4181 7117 4177 7111 4171 7117 4175 7123

$$

WTB

The office that day

Everything else NWS Boston/Norton, MA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 11, 8:32 PM EDT	Areal Flood Advisory	BOX	Bristol, Norfolk	58 min
Aug 11, 8:45 PM EDT	Areal Flood Advisory	BOX	Essex, Franklin, Hampshire, Middlesex, Worcester	2 hr
Aug 11, 10:33 PM EDT	Areal Flood Advisory	BOX	Franklin, Worcester	117 min
Aug 12, 12:24 AM EDT	Areal Flood Advisory	BOX	Middlesex, Worcester	2 hr
Aug 12, 2:36 AM EDT	Areal Flood Advisory	BOX	Bristol	54 min
Aug 12, 2:51 AM EDT	Coastal Flood Advisory	BOX	Barnstable, Essex, Nantucket, Norfolk, Plymouth, Suffolk	24 hr
Aug 12, 5:07 AM EDT	Special Marine Warning	BOX		53 min
Aug 12, 6:31 AM EDT	Areal Flood Advisory	BOX	Essex, Middlesex, Norfolk, Suffolk	59 min
Aug 12, 7:46 AM EDT	Areal Flood Advisory	BOX	Essex, Middlesex, Suffolk	59 min
Aug 12, 8:15 AM EDT	Areal Flood Advisory	BOX	Bristol, Plymouth	60 min
Aug 12, 8:46 AM EDT	Areal Flood Advisory	BOX	Essex, Middlesex, Suffolk	119 min
Aug 12, 9:53 AM EDT	Areal Flood Warning	BOX	Essex	112 min
Aug 12, 10:11 AM EDT	Flash Flood Warning	BOX	Essex, Middlesex	4 hr
Aug 12, 10:55 AM EDT	Areal Flood Advisory	BOX	Bristol	2 hr
Aug 12, 11:07 AM EDT	Dense Fog Advisory	BOX	Norfolk, Plymouth, Suffolk	3 hr
Aug 12, 3:18 PM EDT	Areal Flood Advisory	BOX	Bristol, Norfolk, Worcester	35 min
Aug 12, 3:28 PM EDT	Areal Flood Advisory	BOX	Worcester	62 min
Aug 12, 4:04 PM EDT	Areal Flood Advisory	BOX	Bristol	56 min

Nearby

Flash Flood Warnings in Massachusetts, 2018 Every flash flood warning in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.